Wales had the lowest gross average weekly earnings in Great Britain last year, a study has shown.

The report found that the average pay in Wales was £539, compared with £622.50 across Britain.

Across North Wales in 2013, there were weekly average wages of £491.20 in Gwynedd, £499.40 on Anglesey, £507.50 in Wrexham, £516.90 in Conwy, £555.70 in Denbighshire and £573.50 in Flintshire. Across all of Wales, average earnings ranged from £586.80 in Cardiff to £468.40 in Blaenau Gwent.

It comes as a study by Social Market Foundation, which centres on the destructive effects of low-pay on the UK economy, calls for radical measures to boost skills and improve workers’ earnings. It warns that low pay is hurting Britain’s productivity, with tax credits worth £21bn going to working households each year.

The report argues that the skills of low-paid workers must be boosted for the UK to compete against international rivals and proposes money should be made available to employers to fund skills training and qualifications for 2.9 million workers.

The SMF report, Making Progress, claims that across the UK there are “one in eight workers over the age of 25 over who remain stuck in low pay for at least 12 months”. It argues those who receive training are “almost twice as likely to progress up the occupational ladder as those who do not receive training”.

Former Swansea University economist John Ball said there was a clear link between skills and earnings but the key driver for improved wages was a robust economy.

He said: “There’s no miracle here. A healthy economy builds up wages.”

The report's analysis of Welsh adults aged 25-plus, who were in employment between 2002-03 and 2012-13, suggests that 25% of these workers are low-paid and 12% are “stuck” in long-term low pay. The SMF has calculated 22% of the total UK workforce are low paid.

It found the “proportion of employees on low pay in the private sector (27%) is far higher than the proportion in the public sector (9%)”.

The think tank estimates the measures proposed could see the “take-home pay of a single adult currently on low pay increasing by £555 per year”. The low pay threshold has been defined as £7.62 or “hourly wages below two thirds of the national median wage”.

The report warns that “the proportion of those who start off in low pay and remain stuck has grown significantly: from around 58% in 2005 to almost 75% in 2013. Between 2012 and 2013, some 2.9 million workers were on low pay and had been for at least one year.”

Dr Ball said there was an “argument” about the impact of the minimum wage, saying: “There’s evidence the national minimum wage is actually driving down wage rates. Now employers offer a flat rate to everybody so people with greater skills or experience are not being rewarded."